1. Field of the Invention
The invention relates to a security element for protecting objects of value, which has a liquid-crystalline material. Furthermore, the invention relates to an object of value, a transfer material and method for producing such security elements and objects of value as well as a method for checking such a security element or object of value.
2. Background of the Art
An object of value within the terms of the invention can be any object to be protected, such as for example trademarked products or documents of value. Objects of value within the terms of the present invention are, in particular, security documents such as bank notes, but also share certificates, deeds, stamps, checks, check cards, credit cards, identity documents, passports, admission tickets, tickets, flight tickets and the like as well as labels, seals, packagings, security paper or other elements for the product protection. The simplifying term “object of value” or “security element” therefore in the following always includes documents of the mentioned type.
From DE 199 41 295 A1 a security element with liquid-crystalline material is known, which has thermochromic properties. Upon heating the thermochromic liquid-crystalline material changes its color or becomes transparent, so that the security element can be recognized as such by a viewer.